Dosing device for an infusion system and method thereof

ABSTRACT

A dosing device for an infusion system comprises a dosing unit having a variable volume and at least one opening in fluid connection with the variable volume, through which opening the variable volume can be filled with a substance or the substance can be dispensed from the variable volume. The dosing device is operable in a first state for filling the substance from a supply conduit, in a second state for preventing filling and dispensing, or in a third state for dispensing through a dispensing conduit. No direct fluid connection exists between the supply conduit and the dispensing conduit at any time. Methods for dosing a substance with the dosing device.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is filed under 35 U.S.C. §111(a) as a divisionalof U.S. application Ser. No. 12/559,851 filed Sep. 15, 2009, now U.S.Pat. No. 7,955,302 which is a continuation of International ApplicationNo. PCT/EP2008/001516, with an international filing date of Feb. 26,2008, which claims priority under 35 U.S.C. §119 to European PatentApplication No. 07104240.2, filed Mar. 15, 2007.

TECHNICAL FIELD

The described embodiments relate to a dosing and conveying device and inparticular to a device for dosing a substance to be dispensed.

BACKGROUND

CH 688 224 A5 discloses an implantable device for dispensingpharmaceutical fluids in the human or animal body in doses, wherein theimplantable unit comprises: a cam-controlled, valve-less axial pistonpump comprising a piston which can be rotary-driven and axiallydisplaced; a fluid reservoir which is connected to the suction side ofthe pump; and a rotary drive which is connected to the piston and can becontrolled, wherein a suction opening and a pressure opening are eacharranged on a lower end of a cylinder, and the two openings liediametrically opposite each other and run in the same axis.

U.S. Pat. No. 6,010,485 discloses a working cylinder having a similardesign to that in CH 688 224 A5.

U.S. Pat. No. 6,749,587 B2 discloses a modular infusion apparatuscomprising a measuring portion which can directly control the fluid flowbetween a reservoir and a cannula. If the reservoir is kept at ambientpressure, the measuring portion can comprise a peristaltic mechanism, adisplacement pump or other pump device.

U.S. Pat. No. 4,643,723 discloses a device for administering insulin toa patient, wherein a piston is arranged in a pump chamber, a cannula isconnected to the pump chamber, and a piston rod is connected to thepiston. When the piston is retracted, the reservoir is connected to thepump chamber in order to fill up the pump chamber, and when the pistonis moved forwards, the passage from the reservoir to the pump chamber isclosed by means of a valve, such that the substance can be administeredvia a cannula.

WO 93/04714 and the corresponding EP 0 600 948 B1 disclose a fluidmeasuring element for an implantable administering system which iscoupled between a pressurized fluid source and an outlet opening, inorder to provide discrete flow pulses at a predetermined rate.

US 2004/0069044 A1 discloses a device for measuring a volume of a drug.The device comprises a first chamber which contains the fluid drug, ameasuring chamber which is in fluid connection with the first chamber,and a measuring array.

U.S. Pat. No. 5,207,666 discloses a fluid measuring apparatus forimplantable drug administering systems, which can be arranged between apressurized fluid source and an outlet opening, in order to providediscrete flow pulses at a predetermined rate.

US 2005/0159708 A1 discloses an infusion pump for administering a fluidin doses, wherein a piston is permanently pressurized by means of aspring and acts on a drug container which dispenses the substancethrough a dispensing opening towards a control valve, in order to doseit.

EP 1 633 417 B1 discloses a dispensing apparatus comprising a storagechamber and an injection chamber which are coupled via a fluidconnection and in each of which plungers are arranged.

There remains a need for a dosing device for an infusion system thatenables a substance to be dosed precisely and dispensed simply.

SUMMARY

Embodiments of a dosing device for an infusion system comprise a dosingunit having a variable volume. The variable volume may comprise, forexample, a cylinder comprising a piston that moves in the cylinder tocause an increase or decrease of the volume of the cylinder. The dosingdevice comprises at least one supplying/dispensing port. In someembodiments, the supplying/dispensing port may be a single port, such asa single opening, and the single opening may be disposed, for example,on the cylinder, on a part of the port, or on a sleeve. In someembodiments, the single port may remain closed except during supply anddispensing operations. Through the supplying/dispensing opening, thevariable volume of the dosing unit can be filled with the substance tobe dispensed. The substance may be dispensed, for example, from astorage container such as for example an ampoule, when the volume of thedosing unit is increased. When the variable volume of the filled dosingunit is decreased again, the substance which is to be dispensed in dosescan be outputted again through the dispensing opening. The dosing deviceis preferably designed such that the supplying/dispensing port can bealternately connected to a storage container, such as for example anampoule, and to a dispensing or administering unit such as, for example,an infusion set.

In an embodiment of a method for dosing a substance to be dispensed froma storage container or a reservoir, the substance is moved from thestorage container or reservoir via or through a single port or openinginto a dosing unit having a variable volume. The variable volumeenlarges during dosing, for example, and decreases in volume duringdispensing, for example. Once the variable volume has been filled, theport or opening is connected to a dispensing conduit and the variablevolume containing the substance is then decreased in volume to dispensethe substance in doses through the port or opening. In some embodiments,after the variable volume has been filled with the substance to bedispensed, the dosing unit may be displaced or rotated to decouple theopening of the dosing unit from the supply conduit and to connect thedosing unit to the dispensing conduit.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described below on the basis of example embodiments,wherein:

FIGS. 1A, 1B, 1C illustrate an example operational sequence for dosingusing the dosing device;

FIG. 2 shows one embodiment of the dosing device;

FIGS. 3A-3I show an embodiment of a cyclic process for using the dosingdevice; and

FIGS. 4A-4I show a further embodiment of a cyclic process for using thedosing device.

DETAILED DESCRIPTION

Embodiments of a dosing device for an infusion system comprise a dosingunit comprising a variable volume. The variable volume may comprise, forexample, a cylinder comprising a piston that moves in the cylinder,thereby increasing or decreasing the volume of the cylinder. The dosingdevice comprises a supplying/dispensing port. In some embodiments, thesupplying/dispensing port may be a single port, such as a singleopening. The single opening may be disposed, for example, on thecylinder, on a part of the port, or on a sleeve. In some embodiments,the single port may remain closed except during supply and dispensingoperations. Through the supplying/dispensing opening, the variablevolume of the dosing unit can be filled with the substance to bedispensed. The substance may be dispensed, for example, from a storagecontainer such as for example an ampoule, when the volume of the dosingunit is increased. When the variable volume of the filled dosing unit isdecreased again, the substance which is to be dispensed in doses can beoutputted again through the dispensing opening. The dosing device ispreferably designed such that the supplying/dispensing port can bealternately connected to a storage container, such as for example anampoule, and to a dispensing or administering unit such as, for example,an infusion set.

It is thus possible to prevent leakage and the unintentional oruncontrolled passage of a substance from a reservoir to a dispensingunit such as an infusion set, because the dosing unit is coupled eitherto the reservoir only or to the administering device only. The reservoiris thus completely decoupled from the administering unit, such that thereservoir is never directly connected to the outlet. The substance canbe dispensed so as to be precisely dosed by a dosing device,independently of the design and size of a reservoir or storagecontainer. Also, if a single supplying/dispensing opening is used, thedosing unit exhibits a relatively small leakage or sealing risk.

In some embodiments, the supplying/dispensing port may comprise aplurality of openings that may be connected to an external port alwaysand in such a way that the dosing unit is either only being filled oronly being emptied through all or some of the openings. By such aconfiguration it is not possible to simultaneously receive and dispensea substance. The connection or access or hole of the dosing unit thatacts as inlet or outlet, alternatively the plurality of connections oraccesses or holes of the dosing unit that simultaneously act as an inletor outlet, can be coupled such that they can either be coupled to areservoir (and act as an inlet for the dosing unit) or can be coupled toan administering device, such as for example an infusion apparatus, andso act as an outlet for the dosing unit. In example embodiments, theports of the dosing unit may be sealed when a substance is not beingreceived or dispensed.

In some embodiments the openings may be actively sealed in a restingposition between dispensing and receiving a substance. The activesealing may be accomplished, for example, by a sealing element that canbe displaced.

In some embodiments the dosing unit may be displaced or rotated to beconnected to one of two or more external ports to fill the dosing unitor to dispense and relay the substance dispensed from the dosing unit,depending on the displaced position or rotational position. One or moreof the external ports also may be disposed on the dosing unit in such away that the external ports can be displaced or rotated. In exampleembodiments, the ports that can be displaced may be alternatelyconnected to the supplying/dispensing opening of the dosing unit, forexample. A valve effect can thus be obtained by a kind of switchingvalve.

Some embodiments of the dosing device may comprise a motor configured tomove, or for example, to rotate or displace the dosing unit or thesupplying/dispensing port of the dosing unit. The motor canalternatively or additionally be used to move (for example, to displaceor rotate) the external supplying/dispensing ports so as to alternatelyconnect the supplying/dispensing ports to the supplying/dispensingopening of the dosing unit. The motor or an additional motor can be usedto move the piston to shrink or enlarge the variable the volume. Thepiston of the cylinder is preferably designed to be moveable preciselyto a predetermined position within the cylinder. For example, the pistonmay be moveable exactly to a predefined maximum drawn-out position ofthe piston still situated within the cylinder. Thereby, unlike in known,so-called “single-stroke” methods, in the present embodiments it ispossible to use only some of the variable volume for dosing.

In some embodiments the connecting points or connecting conduits thatlead to the supplying/dispensing port of the dosing unit comprise atleast one valve each. Alternatively, only a single valve may beprovided, for example, in the supply conduit, in the dispensing conduit,or in the supplying/dispensing port. Such a valve in one or both of theconduits, for example as a reflux valve, can ensure that a substance tobe dispensed in doses is conveyed in only one direction. Thereby,backflow of the substance in the opposite direction is inhibited orprevented.

In example embodiments, the valve or valves used on or in the supplyconduits, the drainage conduits, the dosing unit, or any combinationthereof, can be reflux valves that enable the flow of a substance orfluid in only one direction. Alternatively, the valves can be designedas pressure-relief valves that enable the passage of a material or fluidonly when a minimum pressure is applied.

The storage container that contains the substance to be dispensed can bepressurized or non-pressurized. In example embodiments, the storagecontainer may be an ampoule, for example. The ampoule may comprise apressurized stopper that acts on the substance to be dispensed, suchthat the substance to be dispensed may be dosed without requiringadditional energy to dispense the substance from the ampoule, to dosethe dosing unit, to refill the dosing unit, or any of these. In someembodiments, the stopper may be pressurized by means such as, forexample, a spring or a pressurized gas. Alternatively, the storagecontainer may comprise an elastic region or may be formed entirely of anelastic material. In example embodiments, the storage container may beconfigured as a pouch filled with the substance to be dispensed. Todisplace and dispense the substance contained in the storage container,in example embodiments a force or pressure can act on the elastic regionor pouch by means of a spring. The spring may be enabled by the dosingdevice downstream of the storage container.

In some embodiments, the storage container or reservoir may beconfigured such that a positive pressure may be applied at an outlet ordispensing opening of the reservoir. In example embodiments, thepositive pressure at an outlet or opening may be achieved by containersor pouches that are pressurized or charged with a force. Alternatively,the positive pressure may be achieved by an active drive mechanism thatacts on a displacement element of the reservoir or on the reservoiritself.

In some embodiments, the dosing device may comprise at least one sensorfor checking the functional capability or determining a malfunction.Examples of such sensors include, but are not limited to, a leakagesensor, a galvanic or conductance sensor, a bubble sensor, a pressuresensor, or a force sensor. Such sensors are operative to determine, forexample, whether a substance or fluid has escaped from the dosingdevice, whether the substance to be dispensed contains bubbles, orwhether an occlusion is present. In further embodiments, said at leastone sensor may be connected to a warning or alarm indicator or to acontroller of the dosing device. The indicator or controller may beconfigured to switch off the dosing device when a malfunction isdetermined. Alternatively, the indicator or controlled may be configuredto output an alarm signal when a fault in the dosing device isdetermined. Example alarm signals include, for example, an optical oracoustic alarm signal.

In some embodiments, the dosing device, the connecting conduits (forexample, the supply conduit or the dispensing conduit), or both, maycomprise a material that is permeable to gas or air. If air or a gas ispresent in the substance to be dispensed, then a gas-permeable orair-permeable supplying tube that connects the dosing device to thestorage container upstream of dosing can enable the gas in the substanceto escape when the substance is guided through said conduit. Thereby, nogas pockets will be present in the substance in the dosing unit.

In some embodiments, a seal such as, for example, a sealing collar, maybe disposed on the dosing device to seal off the supplying/dispensingport of the dosing unit when the port is not connected to a supplyconduit or a dispensing conduit. The port is not connected to a conduit,for example, when the port is rotated together with the dosing unit fromthe connection to the supply conduit to the connection to the dispensingconduit.

FIGS. 1A-1C show a non-limiting, example embodiment of a dosing device1. The dosing device 1 comprises a dosing unit 2, shown in the exampleembodiment to be configured as a cylinder, comprising asupplying/dispensing port (configured as a single opening 2 a) disposedon one side of the dosing unit 2. In an initial configuration shown inFIG. 1A, before the dosing unit 2 is filled, the single opening 2 a isconnected to a supply conduit 4, which is connected to a reservoir (notshown), for example a pressurized reservoir, which contains a substanceto be dispensed in doses, such as for example insulin. In the exampleembodiment, a movable piston 3 is arranged in the dosing unit 2.

FIG. 1B shows the state of the embodiment of the dosing device 1 fromFIG. 1A, after the dosing unit 2 has been dosed. The dosing unit 2 maybe dosed, for example, by retracting the piston 3 within the dosing unit2 to introduce a substance through the supply conduit 4, into thevariable volume 6 of the dosing unit 2. Once the filling process hasbeen completed, the dosing unit 2 in FIG. 1B has already been rotatedslightly about its longitudinal axis, as indicated by the arrow, suchthat the single opening 2 a of the dosing unit 2 is no longer connectedto the supply conduit 4 or is no longer in fluid communication with thesupply conduit 4. In the state shown in FIG. 1B, the single opening 2 ahas been displaced or rotated toward a dispensing conduit 5, and thesingle opening 2 a is sealed by means of a seal 7 that abuts the dosingunit 2.

If the dosing unit 2 is rotated until the single opening 2 a abuts thedispensing conduit 5, as shown in FIG. 1C, the substance contained inthe variable volume 6 can be dispensed to the dispensing conduit 5through the single opening 2 a by sliding the piston 3 into the dosingunit 2. The dispensing conduit 5 may be connected to an infusion set(not shown) or needle (not shown). In example embodiments, after thesubstance contained in the variable volume 6 of the dosing unit 2 hasbeen partially or completely dispensed, the dosing unit 2 may be rotatedwith the piston 3 completely slid into the dosing unit 2. After such arotation, the single opening 2 a again abuts the supply conduit 4, asindicated in FIG. 1A by the state (4), so that the cycle shown in FIG. 1may be repeated.

FIG. 2 shows an example embodiment of a dosing device 1, wherein thedosing device 1 comprises a dosing unit 2. As shown in the exampleembodiment, the dosing unit 2 may be rotatable. The dosing unit 2 maycomprise, for example, a plastic or an elastic material. The dosing unit2 is disposed between supply conduit 4 and dispensing conduit 5. Supplyconduit 4 and dispensing conduit 5 may comprise, for example, an elasticmaterial. Additionally, the dosing unit 2 may be disposed within asealing sleeve (not shown), for example, and the sealing sleeve maycomprise, for example, two openings. When the single opening 2 a, whichmay be disposed on a lateral surface or on the cylinder casing, isconnected to the supply conduit 4, the variable volume 6 within thedosing unit 2 can be loaded with a substance by retracting the piston 3to draw the substance through the supply conduit 4. In some embodiments,the single opening 2 a can be a simple hole in the dosing unit 2 that issealed by the elastic property of the material (such as plastic, forexample) of the dosing unit 2. In such a case, the substance can passthrough the single opening 2 a only when a pressure or suction acts onthe substance, such as for example when the piston 3 is drawn out of thedosing unit 2 or when the piston 3 is slid into the dosing unit 2.

In some embodiments, the dosing variable volume of the dosing unit maybe incrementally varied, for example in steps or increments. In exampleembodiments, wherein the dosing unit comprises a singlesupplying/dispensing port, the single supplying/dispensing port may bedisposed asymmetrically. In example embodiments, wherein two or moresupplying/dispensing ports are present that can be alternately closed oropened, for example, the supplying/dispensing ports also can be arrangedasymmetrically. Each supplying/dispensing port also can be disposed as asimple opening in the dosing unit, such as for example a cylinder. Asused herein, the terms “asymmetrical port” and “asymmetrical opening”refer to an opening in the dosing unit or, for example, a cylinder,either of which changes its position about an axis of symmetry when thedosing unit is moved, displaced, or rotated. In example embodiments, anasymmetrical opening can be disposed on the end-facing side of acylinder, for example, provided it does not lie in the center of theend-facing side but, rather, is offset from the center of the end-facingside. In further example embodiments, the asymmetrical opening can bedisposed laterally on the dosing unit or in the cylinder casing.

Once the dosing unit 2 has been dosed through the passage of thesubstance through the single opening 2 a into the dosing unit 2 via thesupply conduit 4, the dosing unit 2 is rotated such that the singleopening 2 a of the dosing unit 2 is connected to the dispensing conduit5. In the example embodiment, the dosing unit 2 is rotated by 180° aboutits longitudinal axis. In this state, the piston 3 can be slid back intothe dosing unit 2, so as to displace the substance contained in thedosing unit 2. The substance so displaced is dispensed through the open(and self-closing) single opening 2 a of the dosing unit 2 to thedispensing conduit 5, which is connected to an infusion set (not shown).The dosing unit 2 then can be rotated back or rotated further until thesingle opening 2 a of the dosing unit 2 is returned to fluid connectionwith the supply conduit 4 and is thereby readied to receive another doseof the substance through the supply conduit 4.

FIGS. 3A-3H show an example of a cyclic operational sequence for dosinga substance by means of an embodiment of the dosing device 1. Ingeneral, the dosing device 1 is operable in one of three states. FIGS.3A, 3B, and 3C illustrate a first state, in which a substance may besupplied from, for example, a supply conduit 4 to the variable volume 6through a single opening 2 a. FIGS. 3D and 3H illustrate a second state,in which passage of the substance through the single opening 2 a isprevented. FIGS. 3E, 3F, and 3G illustrate a third state, in which thesubstance may be dispensed from the variable volume 6 through the singleopening, for example, to a dispensing conduit 5 connected to adispensing unit (not shown) of an infusion system (not shown). Thedosing unit may be rotated, displaced, or both, to select the firststate, the second state, or the third state at any given time. Startingfrom an initial position in FIG. 3A, the dosing unit 2 is empty and thepiston 3 is completely or almost completely retracted into the dosingunit 2 toward a supplying/dispensing port (configured as a singleopening 2 a) on the end-facing side of the dosing unit 2. The dosingunit 2 is filled gradually through the supply conduit 4, which isdesigned to be permeable to air. As shown in FIG. 3B, the piston 3 ismoved within the dosing unit 2 in the direction shown by the arrow,thereby enlarging the variable volume 6. The enlargement of the variablevolume 6 results in a negative pressure in the dosing unit 2. Thenegative pressure causes the substance to be supplied from a reservoir(not shown) and be drawn through the supply conduit 4 or introduced intothe dosing unit 2. The dosing unit 2 or the single opening 2 a ispositioned or rotated to lie as close as possible to the front of theopening of the supply conduit 4, such that a fluid connection is createdfrom the supply conduit 4 to the variable volume 6 through the singleopening 2 a.

In the embodiment shown, sealing elements 7, 8 may be disposed betweenthe supply conduit 4 and dispensing conduit 5 and the dosing unit 2 onthe front side, the connecting side, the contact side, or anycombination of these. The sealing elements 7, 8 may be arranged aroundthe openings of the supply conduit 4 and the dispensing conduit 5 toprevent escape of the substance or fluid flowing in the supply conduit 4or in the dispensing conduit 5. In some embodiments, the sealingelements 7, 8 may comprise, for example, disc-shaped or annularelements, as shown in FIG. 3I, and the elements may comprise, forexample, an elastic material. In examples of such embodiments, thedosing unit 2 or an end-facing side of the dosing unit 2 is able toslide easily over the sealing elements 7, 8.

As can be seen from FIG. 3C, the dosing unit 2 is completely filled whenthe piston 3 has been drawn out up to a maximum position. In the shownexample embodiment, wherein the dosing unit is configured as a cylindercomprising a piston, this maximum volume of the variable volume 6 of thedosing unit is referred to as V_(cylinder, max). When the dosing unit isconfigured as a cylinder comprising a piston, the maximum volume of thevariable volume (V_(cylinder, max)) may be defined as the volume of thecylinder when the piston is drawn out as far as desirable for theparticular dosing application, for example, completely drawn out oralmost completely drawn out. In some embodiments, the dosing device maybe configured such that V_(cylinder, max) is smaller than 0.1 times thevolume of the storage container or a reservoir (V_(reservoir)) in whichthe substance to be dispensed is contained. In some embodiments, themaximum volume V_(cylinder, max) may be substantially larger than thevolume of a minimum dose to be dispensed (V_(dose, min)). For example,V_(cylinder, max) may be twice V_(dose, min) or even, for example, tentimes V_(dose, min). In some embodiments, the maximum volume of thedosing unit V_(cylinder, max) may be equal to the minimum volume of thedose to be dispensed V_(dose, min) multiplied by the square root of theratio of the volume of the reservoir V_(reservoir) to the minimum volumeof the minimum dose to be dispensed V_(dose, min), according to thefollowing equation:V _(cylinder,max) =V _(dose,min)×√{square root over ((V _(reservoir) /V_(dose,min)))}.

Thus, in some embodiments the dosing device may be configured such that:

x×V_(dose, min)<V_(cylinder, max)<y×V_(reservoir), where 2<x<10 and0.1<y<0.5.

In some embodiments, the ratio of the inner diameter of a cylindricaldosing unit to the length of the cylinder may be equal to or about 1:4.

In the continuation of the process, referring now to FIG. 3D, the dosingunit 2 then is rotated about its longitudinal axis to switch from theprocess of filling the dosing unit 2 to the process of dispensing fromthe dosing unit 2. In this stage, the dosing unit 2 is rotated until thesingle opening 2 a is in front of the dispensing conduit 5, as shown inFIG. 3E, such that a fluid connection is established between thevariable volume 6 of the dosing unit 2 and the dispensing conduit 5through the single opening 2 a.

When the piston 3 is now retracted back into the dosing unit 2, as shownin FIG. 3F, the substance contained in the variable volume 6 isdispensed, for example to an infusion set, through the single opening 2a and the dispensing conduit 5. The piston 3 can be retracted until thedosing unit 2 is completely emptied or, as shown in FIG. 3G, almostcompletely emptied. Thereby, the piston 3 is maximally retracted intothe dosing unit 2 on reaching a front end or a dispensing end of thedosing unit 2.

The dosing unit then can be switched again, as shown in FIG. 3H, torefill the variable volume 6 after a dispensing process has beencompleted. To switch the dosing device, the dosing unit 2 is rotatedagain, such that the single opening 2 a again lies in front of thesupply conduit 4, as shown in FIG. 3A.

In some embodiments, the rotations of the dosing unit 2 shown in FIGS.3D and 3H, may be made always in the same direction relative to thelongitudinal axis of the cylinder, such as, for example, alwaysclockwise or always counterclockwise. Alternatively, it is also possiblefor the dosing unit 2 to be rotated in a first direction to switch fromthe filling process to the dispensing process (such as, for example, tothe left as shown in FIG. 3D) and to be rotated in the oppositedirection to switch from the dispensing process to the filling process(such as, for example, to the right as shown in FIG. 3H). This isparticularly advantageous when a back-and-forth movement of the piston 3is realized using a single motor and the motor is also used to move thedosing unit 2 back and forth or to rotate the dosing unit 2.

FIG. 3I shows a perspective view of an example embodiment of sealingelement 7, 8 with the passage (sealing element opening 7 a and/or 8 a)arranged in it, to which the supply conduit 4 is connected (in thestates in accordance with FIGS. 3A to 3C), to which the dispensingconduit 5 is connected (in the states in accordance with FIGS. 3E to3G), or both.

FIGS. 4A-4H show an embodiment of an operational sequence similar to theembodiment shown in FIG. 3. A dosing unit 2 comprises twosupplying/dispensing ports for filling and dispensing, configured as asupply opening 4 a and a dispensing opening 5 a. The supply opening 4 aand the dispensing opening 5 a are disposed on one side of the dosingunit 2. The supply opening 4 a and the dispensing opening 5 a can bearranged in many configurations such as, for example, opposite eachother in relation to the center of the dosing unit 2. A sealing element7, continuously through which a sealing element opening 7 a is provided,is disposed in front of the supply opening 4 a and the dispensingopening 5 a of the dosing unit 2. As shown in the figures, the dosingunit 2 is operable in one of three states. In a first state, depicted inFIGS. 4A, 4B, and 4C, the supply opening 4 a is open and the dispensingopening 5 a is closed. In a second state, depicted in FIGS. 4D and 4H,both the supply opening 4 a and the dispensing opening 5 a are closed.In a third state, depicted in FIGS. 4E, 4F, and 4G, the dispensingopening 5 a is open and the supply opening 4 a is closed. The dosingunit 1 may be rotated, displaced, or both, to select the first state,the second state, or the third state at any given time.

An example embodiment of a sealing element 7 is shown in FIG. 4I. Thesealing element 7 can be rotated or moved relative to the dosing unit 2,the supply conduit 4, and the dispensing conduit 5. The dosing unit 2,the supply conduit 4 and the dispensing conduit 5 are preferably in adefined or fixed positional relationship. In the various positions ofrotation of the sealing element 7 with the sealing element opening 7 adisposed therein, supply opening 4 a and dispensing opening 5 a may atany given time be both sealed (as in the switching processes shown inFIGS. 4D and 4H), or be alternately opened (as in the filling process ofFIGS. 4A-4C and the dispensing process of FIGS. 4E-4G).

During the filling process as shown in the sequence of FIGS. 4A, 4B, and4C, the sealing element opening 7 a of the sealing element 7 is disposedin a position at which a fluid connection can be established between thesupply conduit 4 and the variable volume 6. To switch between thefilling process and the dispensing process, the sealing element 7 may berotated about its center axis, as shown in FIG. 4D, until the sealingelement opening 7 a of the sealing element 7 is arranged as shown inFIG. 4E. Namely, the sealing element opening 7 a of the sealing element7 is arranged so that, for example, the supply opening 4 a of the dosingunit 2 is sealed and so that the dispensing opening 5 a of the dosingunit is in fluid connection to the dispensing conduit 5. Thereupon, thedispensing process may be performed as shown in the progression fromFIG. 4E to FIG. 4F to FIG. 4G.

It is then possible to switch from the dispensing process back to thefilling process, as shown in FIG. 4H, wherein the sealing element 7 isrotated so that the sealing element opening 7 a of the sealing element 7is in the position shown in FIG. 4A.

FIG. 4I shows a perspective view of the sealing element 7, comprising asealing element opening 7 a that is offset in the radial direction fromthe center point of the sealing element 7, where the center axis 11 ofthe sealing element intersects the surface of the sealing element 7(depicted as an x).

1. A method for dosing a substance, the method comprising: providing adosing device, the dosing device comprising a dosing unit having avariable volume contained within the dosing unit and at least oneopening in fluid connection with the variable volume, a supply conduitconnected to the dosing unit and in fluid connection to a reservoircontaining the substance, and a dispensing conduit connected to thedosing unit and in fluid connection to a dispensing unit of an infusionsystem, the dosing unit being operable in a first state in which thevariable volume is in fluid connection to the reservoir through the atleast one opening but is not in fluid connection to the dispensingconduit, in a second state in which the variable volume is in fluidconnection to neither the reservoir nor the dispensing conduit, or in athird state in which the variable volume is in fluid connection to thedispensing conduit through the at least one opening but is not in fluidconnection to the reservoir, wherein the dosing unit is operable to bemoved to select the first state, the second state, or the third state;selecting the first state of the dosing unit; filling the substance intothe variable volume through the supply conduit and the single opening,such that the variable volume enlarges while the substance enters thevariable volume; moving the dosing unit so as to move, rotate, ordisplace the at least one opening and select the third state of thedosing unit; and dispensing the substance through the at least oneopening and into the dispensing conduit by decreasing the volume of thevariable volume.
 2. The method of claim 1, wherein the dosing unitcomprises a piston disposed within a cylinder and wherein, during thedispensing, the volume of the variable volume is decreased by moving thepiston.
 3. The method of claim 1, wherein the dosing unit is configuredso that, during the filling or the dispensing, a predeterminedintermediate volume of the variable volume between a minimum volume ofthe variable volume and a maximum volume of the variable volume can begenerated to establish a dose setting, the dose setting defining avolume less than the maximum volume of the variable volume.
 4. Themethod of claim 3, wherein the dosing unit comprises a piston disposedwithin a cylinder and the dose setting is established by moving thepiston to an intermediate position so as to generate the predeterminedintermediate volume of the variable volume.